Electrophotographic photosensitive drum, process cartridge, and electrophotographic image forming apparatus

ABSTRACT

An electrophotographic photosensitive drum usable with an electrophotographic image forming apparatus, includes a non-circular twisted projection having a cross-section with a plurality of corner portions, a non-circular twisted projection being provided at one longitudinal end of the drum, and being engageable with a non-circular twisted hole having a section with a plurality of corner portions, the non-circular twisted hole being disposed at a central portion of a driving rotatable member of a main assembly of the image forming apparatus; and a second electroconductive member contactable with a first electroconductive member electrically connected with a main assembly of the image forming apparatus. The first electroconductive member is disposed in the hole to ground the drum. The second electroconductive member is provided on the projection and is electrically connected with the drum. The contact position between the first and second electroconductive members moves in interrelation with the projection being retracted toward the hole by rotation of the driving rotatable member when the projection is engaged with the projection.

CROSS-REFERENCE TO RELATED APPLICATION

This is a divisional application of application Ser. No. 10/960,117,filed Oct. 8, 2004, pending.

FIELD OF THE INVENTION AND RELATED ART

The present invention relates to an electrophotographic photosensitivedrum, a process cartridge comprising an electrophotographicphotosensitive drum, and an electrophotographic image forming apparatus.

Here, an electrophotographic image forming apparatus means an apparatusfor forming an image on recording medium with the use of one of theelectrophotographic image forming methods. The examples of anelectrophotographic image forming apparatus include anelectrophotographic copying machine, an electrophotographic printer (forexample, a laser printer, an LED printer, etc.), a facsimile apparatus,a word processor, etc.

A process cartridge is a cartridge which is removably mountable in themain assembly of an image forming apparatus, and in which a minimum ofone among a charging means, a developing means, and a cleaning means, asa processing means, and an electrophotographic photosensitive member,are integrally placed so that they can be removably mountable in themain assembly of an image forming apparatus.

A photosensitive drum unit means an electrophotographic photosensitivemember in the form of a drum, employed by the main assembly of anelectrophotographic image forming apparatus.

An electrophotographic image forming apparatus such as a copyingmachine, a laser printer, a facsimile machine, etc., forms anelectrostatic latent image by selectively exposing numerous points ofthe peripheral surface of the electrophotographic photosensitive drumuniformly charged by a charging apparatus. Then, it develops theelectrostatic latent image into a visible image (image formed of toner)by adhering toner to the electrostatic latent image, with the use of thedeveloping apparatus, and yields a copy of an intended image bytransferring the toner image onto a recording medium such as a sheet ofpaper. After the transfer of the toner image, it removes the tonerremaining on the peripheral surface of the electrophotographicphotosensitive drum, with the use of the cleaning apparatus, preparingthe photosensitive drum for the following image formation operation.

In the field of an electrophotographic image forming apparatus employingan electrophotographic image formation process, it has been a commonpractice to employ a process cartridge system, in which anelectrophotographic photosensitive drum, and a single or plurality ofprocessing means, such as a charging apparatus, a developing apparatus,a cleaning apparatus, etc., which act on the electrophotographicphotosensitive drum, are integrally placed in a cartridge removablymountable in the main assembly of an image forming apparatus. Accordingto this process cartridge system, apparatus maintenance can be carriedout by a user by himself, without the need for relying on servicepersonnel, drastically improving an image forming apparatus inoperational efficiency. Thus, a process cartridge system has been widelyused in the field of an image forming apparatus.

An electrophotographic photosensitive drum is structured to allowresidual electric charge to escape from the electrophotographicphotosensitive drum to the main assembly of the image forming apparatus.More specifically, the electrophotographic photosensitive drum comprisesa drum cylinder formed of electrically conductive substance, and a pairof flanges having a shaft portion by which the electrophotographicphotosensitive drum is supported by the frame of a process cartridge orthe main assembly of the image forming apparatus. The flanges areattached to the lengthwise ends of the drum cylinder by being pressedinto the openings of the lengthwise ends of the drum cylinder. One ofthe flanges is provided with an electrically conductive member, which islocated at the center of the flange. This conductive member is providedwith a projection, which contacts the internal surface of the drumcylinder, and a flat portion by which the conductive member of theflange contacts the conductive member on the main assembly side of theimage forming apparatus. According to the prior art, the conductivemember on the main assembly side is kept in contact with the conductivemember of the flange by utilizing the resiliency of a spring or thelike, in order to keep the electrophotographic sensitive drumelectrically connected to the apparatus main assembly (JapaneseLaid-open Patent Application 2000-112200).

SUMMARY OF THE INVENTION

The primary object of the present invention is to provide anelectrophotographic photosensitive drum capable of reliably establishingelectrical connection between it and the main assembly of anelectrophotographic image forming apparatus, a process cartridgecomprising said electrophotographic photosensitive drum, and anelectrophotographic image forming apparatus compatible with saidelectrophotographic photosensitive drum and process cartridge.

Another object of the present invention is to provide anelectrophotographic photosensitive drum capable of wiping itselectrically conductive member in order to be reliably grounded, aprocess cartridge comprising said electrophotographic photosensitivedrum, and an electrophotographic image forming apparatus compatible withsaid electrophotographic photosensitive drum and process cartridge.

Another object of the present invention is to provide anelectrophotographic photosensitive drum capable of rotating the firstand second electrically conductive members together in order to preventthe conductive members from being frictionally worn, a process cartridgecomprising said electrophotographic photosensitive drum, and anelectrophotographic image forming apparatus compatible with saidelectrophotographic photosensitive drum and process cartridge.

According to an aspect of the present invention, there is provided anelectrophotographic photosensitive drum usable with anelectrophotographic image forming apparatus, comprising a non-circulartwisted projection having a cross-section with a plurality of cornerportions, the non-circular twisted projection being provided at onelongitudinal end of the electrophotographic photosensitive drum, andbeing engageable with a non-circular twisted hole having a section witha plurality of corner portions, the non-circular twisted hole beingdisposed at a central portion of a driving rotatable member of a mainassembly of the image forming apparatus; and a second electroconductivemember contactable with a first electroconductive member electricallyconnected with a main assembly of the image forming apparatus, the firstelectroconductive member being disposed in the hole to ground theelectrophotographic photosensitive drum, the said secondelectroconductive member being provided on the projection and beingelectrically connected with the electrophotographic photosensitive drum,wherein a contact position between the second electroconductive memberand the first electroconductive member moves in interrelation with theprojection being moved toward the hole by rotation of the drivingrotatable member when the projection is engaged with the non-circulartwisted hole of the driving rotatable member.

According to another aspect of the present invention, there is providedan electrophotographic photosensitive drum usable with anelectrophotographic image forming apparatus, comprising a non-circulartwisted projection having a cross-section with a plurality of cornerportions, the non-circular twisted projection being provided at onelongitudinal end of the electrophotographic photosensitive drum, andbeing engageable with a non-circular twisted hole having a section witha plurality of corner portions, the non-circular twisted hole beingdisposed at a central portion of a driving rotatable member of a mainassembly of the image forming apparatus; a second electroconductivemember contactable with a first electroconductive member electricallyconnected with a main assembly of the image forming apparatus, the firstelectroconductive member being disposed in the hole to ground theelectrophotographic photosensitive drum, the second electroconductivemember being provided on the projection and being electrically connectedwith the electrophotographic photosensitive drum, wherein while theprojection is in engagement with the hole and is being rotated, thesecond electroconductive member and the first electroconductive memberare integrally rotated while being in contact with each other.

According to a further aspect of the present invention, there isprovided a process cartridge detachably mountable to anelectrophotographic image forming apparatus, the process cartridgecomprising an electrophotographic photosensitive drum; a non-circulartwisted projection having a cross-section with a plurality of cornerportions, the non-circular twisted projection being provided at onelongitudinal end of the electrophotographic photosensitive drum, andbeing engageable with a non-circular twisted hole having a section witha plurality of corner portions, the non-circular twisted hole beingdisposed at a central portion of a driving rotatable member of a mainassembly of the image forming apparatus; and a second electroconductivemember contactable with a first electroconductive member electricallyconnected with the main assembly of the image forming apparatus, thefirst electroconductive member being disposed in the hole to ground theelectrophotographic photosensitive drum, the second electroconductivemember being provided on the projection and being electrically connectedwith the electrophotographic photosensitive drum, wherein a contactposition between the second electroconductive member and the firstelectroconductive member moves in interrelation with the projectionbeing moved toward the hole by rotation of the driving rotatable memberwhen the projection is engaged with the hole of the driving rotatablemember.

According to a further aspect of the present invention, there isprovided a process cartridge detachably mountable to anelectrophotographic image forming apparatus, the process cartridgecomprising an electrophotographic photosensitive drum; a non-circulartwisted projection having a cross-section with a plurality of cornerportions, the non-circular twisted projection being provided at onelongitudinal end of the electrophotographic photosensitive drum, andbeing engageable with a non-circular twisted hole having a section witha plurality of corner portions, the non-circular twisted hole beingdisposed at a central portion of a driving rotatable member of a mainassembly of the image forming apparatus; and a second electroconductivemember contactable with a first electroconductive member electricallyconnected with the main assembly of the image forming apparatus, thefirst electroconductive member being disposed in the hole to ground theelectrophotographic photosensitive drum, the second electroconductivemember being provided on the projection and being electrically connectedwith the electrophotographic photosensitive drum, wherein while theprojection is in engagement with the hole and is being rotated, thesecond electroconductive member and the first electroconductive memberare integrally rotated while being in contact with each other.

According to a further aspect of the present invention, there isprovided a electrophotographic image forming apparatus to which aprocess cartridge is detachably mountable, comprising

-   -   (i) rotational drive member;    -   (ii) a non-circular twisted hole having a cross-section with a        plurality of corner portions, the non-circular twisted hole        being disposed at a central portion of a driving rotatable        member of a main assembly of the apparatus;    -   (iii) a first electrophotographic member electrically connected        with the main assembly of the image forming apparatus;    -   (iv) a process cartridge demountably mounted to a cartridge        mounting portion, the process cartridge including,    -   an electrophotographic photosensitive drum,    -   a non-circular twisted projection having a cross-section with a        plurality of corner portions, the non-circular twisted        projection being provided at one longitudinal end of the        electrophotographic photosensitive drum, and being engageable        with the non-circular twisted hole, and    -   a second electroconductive member contactable with a first        electroconductive member electrically connected with a main        assembly of the image forming apparatus to electrically ground        the electrophotographic photosensitive drum, the second        electroconductive member being provided on the projection and        being electrically connected with the electrophotographic        photosensitive drum,    -   wherein a contact position between the second electroconductive        member and the first electroconductive member moves in        interrelation with the projection being moved toward the hole by        rotation of the driving rotatable member when the projection is        engaged with the hole of the driving rotatable member.

According to a further aspect of the present invention, there isprovided an electrophotographic image forming apparatus to which aprocess cartridge is detachably mountable, comprising

-   -   (i) rotational drive member;    -   (ii) a non-circular twisted hole having a cross-section with a        plurality of corner portions, the non-circular twisted        projection being disposed at a central portion of a driving        rotatable member of a main assembly of the apparatus;    -   (iii) a first electroconductive member electrically connected        the main assembly of said image forming apparatus, the first        electroconductive member being disposed in the hole;    -   (iv) a process cartridge demountably mounted to a cartridge        mounting portion, the process cartridge including,    -   an electrophotographic photosensitive drum,    -   a non-circular twisted projection having a cross-section with a        plurality of corner portions, the non-circular twisted        projection being provided at one longitudinal end of the        electrophotographic photosensitive drum, and being engageable        with the non-circular twisted hole, and    -   a second electroconductive member contactable with a first        electroconductive member electrically connected with the main        assembly of the image forming apparatus to electrically ground        the electrophotographic photosensitive drum, the second        electroconductive member being provided on the projection and        being electrically connected with the electrophotographic        photosensitive drum,    -   wherein while the projection is in engagement with the hole and        is being rotated, the second electroconductive member and the        first electroconductive member are integrally rotated while        being in contact with each other.

These and other objects, features, and advantages of the presentinvention will become more apparent upon consideration of the followingdescription of the preferred embodiments of the present invention, takenin conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic sectional view of the multicolor image formingapparatus in one of the preferred embodiments of the present invention.

FIG. 2 is a schematic sectional view of the image forming apparatus inthe preferred embodiment of the present invention, the front cover ofwhich has been opened to expose the opening through which processcartridges are inserted.

FIG. 3 is an enlarged cross-sectional view of the process cartridge inthe preferred embodiment of the present invention.

FIG. 4 is a perspective view of the process cartridge in the preferredembodiment of the present invention.

FIG. 5 is a perspective view of the process cartridge in the preferredembodiment of the present invention.

FIG. 6 is a schematic sectional view of the main assembly of the imageforming apparatus in the preferred embodiment of the present invention,for describing how the process cartridges are mounted into the mainassembly.

FIG. 7 is a perspective view of the photosensitive drum unit in thepreferred embodiment of the present invention.

FIG. 8 is a combination of a perspective view and sectional views of thephotosensitive drum unit, for describing the steps followed to attachthe drum grounding plate.

FIG. 9 is a detailed vertical sectional view of the drum grounding platein the preferred embodiment of the present invention, describing thestructure thereof.

FIG. 10 is a detailed vertical sectional view of the drum groundingplate in the preferred embodiment of the present invention, describingthe structure thereof.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, the preferred embodiments of the present invention will bedescribed with reference to the appended drawings.

Embodiment 1

(1) General Structure of Image Forming Apparatus

FIG. 1 is a vertical sectional view of the multicolor image formingapparatus in the preferred embodiment of the present invention, showingthe general structure thereof. This multicolor image forming apparatusis a full-color laser beam printer which uses an electrophotographicprocess of a transfer type, and employs a plurality of processcartridges removably mountable in its cartridge compartment. It has aprocess cartridge compartment in which a plurality of process cartridgesare virtually vertically stacked in parallel.

Designated by a referential number 100 is the main assembly of the imageforming apparatus (which hereinafter will be referred to simply asapparatus main assembly), and designated by a referential number 101 isa front cover of the apparatus (which hereinafter will be referred tosimply as front cover). This front cover 101 is hinged to the apparatusmain assembly 100, being enabled to be opened or closed by being rotatedabout the hinge shaft 101 a located at the bottom edge of the frontcover 101. In FIG. 1, the front cover 101 is closed against theapparatus main assembly 100, and in FIG. 2, the front cover 101 has beenopened toward an operator, exposing the opening 91 through which processcartridges are inserted into the apparatus main assembly 100.

Designated by referential numbers 7 a, 7 b, 7 c, and 7 d are fourprocess cartridges (which hereinafter will be referred to simply ascartridges), that is, first to fourth cartridges for forming tonerimages of magenta, cyan, yellow, and black colors, which correspond tothe color components into which the optical image of an intendedfull-color image is separated. These cartridges 7 are stacked inparallel in the direction slightly tilted from the true verticaldirection, in the cartridge compartment of the apparatus main assembly100, being stacked in the listed order, with the cartridge 7 apositioned at the bottom.

Each cartridge 7(a-d) has an electrophotographic photosensitive member,as an image bearing member 1(a-d), in the form of a drum (whichhereinafter will be referred to as photosensitive drum). It also hassuch electrophotographic processing devices as a charging apparatus(charging means) 2(a-d) for uniformly charging the peripheral surface ofthe photosensitive drum 1, a developing apparatus (developing means) 4for developing the electrostatic latent image formed on the peripheralsurface of the photosensitive drum 1 into a toner image (image formed oftoner) by adhering toner to the electrostatic latent image, a cleaningapparatus (cleaning means) 6(a-d) for removing the toner remaining onthe peripheral surface of the photosensitive drum 1 after the transferof the toner image onto a transfer medium (recording medium), etc.

The developers stored in the developing apparatuses 4(a-d) of the firstto fourth cartridges 7(a-d) are magenta, cyan, yellow, and black toners,respectively.

Designated by reference characters 3 a, 3 b, 3 c, and 3 d are fourscanner units which correspond to the four cartridges 7 one for one. Thescanner unit is an exposing means for forming an electrostatic latentimage on the peripheral surface of the photosensitive drum 1, byprojecting a beam of laser light (image forming light) L onto theuniformly charged peripheral surface of the photosensitive drum 1. Morespecifically, the beam of laser light L outputted from the laser diode(unshown) while being modulated with image formation data is reflected(deflected) by the polygon mirror 9(a-d) being rotated at a high speedby the scanner motor (unshown). The reflected beam of laser light L issent through the image forming lens 10(a-d), being thereby focused onthe uniformly charged peripheral surface of the photosensitive drum 1.As a result, numerous points of the uniformly charged peripheral surfaceof the photosensitive drum 1 are selectively exposed, forming anelectrostatic image on the peripheral surface of the photosensitive drum1.

Designated by a reference number 93 is a partitioning wall in theapparatus main assembly 100. It partitions the cartridge compartment, inwhich the four cartridges 7(a-d) are mounted, from the scanner unitcompartment, in which the four scanner units 7(a-d) are located. Thebeam of laser light L outputted from each of the scanner units 7(a-d)enters the corresponding cartridge 7 through the corresponding window95, that is, one of the windows with which the partitioning wall 93 isprovided, and scans the peripheral surface of the correspondingphotosensitive drum 1, selectively exposing the numerous points of theperipheral surface of the photosensitive drum 1.

Designated by a referential number 5 is an electrostatic transferringapparatus (electrostatic transferring means), which is attached to theinward side of the front cover 101. Thus, the front cover 101 is openedor closed, along with this electrostatic transferring apparatus 5,against the apparatus main assembly 100 (FIG. 2). The electrostatictransferring apparatus 5 is provided with an electrostatic transfer belt11, which is circularly driven in contact with all of the photosensitivedrum 1 of the first to fourth cartridges 7 after the front cover 101 isclosed against the apparatus main assembly 100. Designated byreferential numbers 12 a, 12 b, 12 c, and 12 d are four transferrollers, which are placed within the loop formed by the electrostatictransfer belt 11, being positioned so that the electrostatic transferbelt 11 remains pinched between the photosensitive drums 1 of the firstto fourth cartridges 7(a-d), and electrostatic transfer belt 11.

Designated by a reference number 16 is a transfer medium conveyingportion located in the bottom portion of the apparatus main assembly100. It is a portion for causing a transfer of a medium S to theelectrostatic transfer belt 11 of the electrostatic transferringapparatus 5. Designated by a reference number 17 is a sheet feedercassette of the transfer medium conveying portion 16, in which aplurality of transfer media S are stored. Designated by referencenumbers 18 and 19 are a sheet feeder roller (semicylindrical roller),and a pair of registration rollers, respectively.

Designated by a referential number 20 is a fixation station located inthe top portion of the apparatus main assembly 100. It fixes to thetransfer medium S a plurality of toner images different in color havingbeen transferred onto the transfer medium S. It has a rotational heatroller 21 a, a pressure roller 21 b kept pressured upon the heat roller21 a to apply pressure to the transfer medium S, etc. Designated byreferential numbers 23 and 24 are a pair of discharge rollers, and adelivery tray portion which catches the transfer medium S on which animage has just been formed.

The photosensitive drums 1 in the first to fourth cartridges 7 aresequentially rotated in the counterclockwise direction indicated by anarrow mark with predetermined timings of the image formation sequence.Then, the scanner units 3(a-d) are sequentially driven in synchronismwith the rotations of the photosensitive drums 1 of the correspondingcartridges 7. Further, the electrostatic transfer belt 11 of theelectrostatic transferring apparatus 5 is circularly driven by a driverroller 13 in the clockwise direction indicated by an arrow mark at theperipheral velocity matching the peripheral velocities of thephotosensitive drums 1.

As each photosensitive drum 1 is rotated as described above, itsperipheral surface is uniformly charged (primary charge) by the chargingapparatus 2(a-d) to predetermined polarity (negative in this embodiment)and potential level. The charged peripheral surface of thephotosensitive drum 1 is exposed to the beam of laser light L outputtedfrom the scanner unit 3 while being modulated with the image formationdata. As a result, an electrostatic latent image in accordance with theimage formation data is formed on the peripheral surface of thephotosensitive drum 1.

The electrostatic latent image is developed (in reverse with use oftoner, inherent polarity of which is negative, in this embodiment) intoa toner image (image formed of toner) by the developing apparatus 4. Asa result, toner images of magenta, cyan, yellow, and black colors areformed on the peripheral surfaces of the photosensitive drums 1 of thefirst to fourth cartridges 7(a-d), respectively, with predeterminedsequence control timings.

Meanwhile, the feed roller 18 of the transfer medium conveying portion16 is rotationally driven with the predetermined sequence controltiming, feeding the transfer mediums S into the apparatus main assembly100 from the cassette 17, while separating them one by one. As theleading end of each transfer medium S is conveyed, it comes into contactwith the nip formed by the pair of registration rollers 19 which are notbeing rotated. As it comes into contact with the pair of registrationrollers 19, it is temporarily kept on standby, arcing upward. Then, theregistration rollers 19 begin to be rotationally driven in synchronismwith the circular movement of the electrostatic transfer belt 11 and themovement of the line of the peripheral surface of the photosensitivedrum 1, at which the toner image begins to be written. As a result, thetransfer medium S is conveyed to the tension roller side of the upwardlymoving side of the electrostatic transfer belt 11, and iselectrostatically adhered to the surface of the electrostatic transferbelt 11 by the static electricity naturally induced in the electrostatictransfer belt 11, being thereby reliably held to the electrostatictransfer belt 11. Then, the transfer medium S is conveyed to thetransfer station, or the most downstream station, by the movement of theelectrostatic transfer belt 11. The transfer medium conveying portion 16may be provided with a charging means, such as an electrostatic adhesionroller, or the like, for intentionally charging the transfer medium Sand/or electrostatic transfer belt 11 in order to electrostaticallyadhere the recording medium S to the electrostatic transfer belt 11.

While being conveyed as described above, the transfer medium Ssequentially receives in layers the toner images formed on theperipheral surfaces of the photosensitive drums 1; the toner imagesformed on the peripheral surfaces of the photosensitive drums 1 of thefirst to fourth cartridges 7 are sequentially transferred in layers ontothe recording medium S by the electric field formed between thephotosensitive drums 1 and corresponding transfer rollers 12. In thisembodiment, bias with the positive polarity is applied to each transferroller 12, causing thereby positive electric charge to be applied to thetransfer medium S through the electrostatic transfer belt 11, generatingthe electric field, which transfers the toner images on thephotosensitive drums 1, which are positive in polarity, onto thetransfer medium S being conveyed in contact with the photosensitivedrums 1(a-d), during the image transfer operation.

More specifically, the transfer medium S is electrostatically adhered tothe surface of the electrostatic transfer belt 11, being held thereto,and is conveyed upward by the rotation of the electrostatic transferbelt 11. While the transfer medium S is conveyed upward by theelectrostatic transfer belt 11 as described above, it sequentiallyreceives in layers the toner images of magenta, cyan, yellow, and blackcolors formed on the peripheral surfaces of the photosensitive drums 1of the first to fourth cartridges 7; it receives one toner image in eachtransfer station. As a result, an unfixed full-color toner image issynthesized on the surface of the recording medium S.

After the reception, in layers, of the four toner images different incolor, the transfer medium S is separated from the electrostatictransfer belt 11 by the curvature of the driver roller 13 of thetransfer medium conveying portion 16, and is conveyed into the fixationstation 20. In the fixation station 20, the transfer medium S isconveyed through the fixation nip formed by the rotating heat roller 21a, and pressure roller 21 b rotated while being pressed against the heatroller 21 a. As a result, the plurality of toner images different incolor are fixed to the transfer medium S by the heat and pressureapplied to the transfer medium S by the pair of rollers 21 a and 21 b.After the fixation of the toner images to the transfer medium S in thefixation station 20, the transfer medium S is discharged by the pair ofdischarge rollers 23 into the external delivery tray 24 of the apparatusmain assembly 100, with the image bearing surface of the transfer mediumS facing downward.

The residues such as the toner remaining on the peripheral surface ofthe photosensitive drum 1 in each of the first to fourth cartridges 7after the transfer of the toner image onto the transfer medium S areremoved by the cleaning apparatus 6, and the photosensitive drum 1 isused for the following image formation.

(2) Process Cartridge 7

FIG. 3 is an enlarged cross sectional view of the cartridge 7, and FIGS.4 and 5 are schematic perspective views of the cartridge 7.

In this embodiment, the photosensitive drum 1 is an integral part of thecartridge 7, and therefore, it is removably mounted into the apparatusmain assembly 100 as the cartridge 7 is removably mounted into theapparatus main assembly 100.

In the following description of this embodiment, the widthwise directionof the cartridge 7 or the structural components thereof is the directionparallel to the direction in which the cartridge 7 is mounted into, orremoved from, the apparatus main assembly 100, whereas the lengthwisedirection means the direction intersectional (perpendicular) to thedirection in which the cartridge 7 is mounted into, or removed from, theapparatus main assembly 100. The front side of the cartridge 7 means theside of the cartridge 7 which faces the direction from which thecartridge 7 is inserted into the apparatus main assembly 100, or thedirection toward which the cartridge 7 is removed from the apparatusmain assembly 100; in other words, it is the side of the cartridge 7where the hole of the cartridge 7 through which the photosensitive drum1 is exposed is present. The rear side of the cartridge 7 means the sideopposite to the front side. The left and right of the cartridge 7 meansthe left and right sides, as seen from the front side of the cartridge7. The top and bottom sides of the cartridge 7 means the sides whichwill be on the top and bottom sides, respectively, after the mounting ofthe cartridge 7 into the apparatus main assembly 100.

The first to fourth cartridges 7(a-d) are the same (in structure) exceptfor the developers stored in the toner container portions (developerstorage portions) of the developing apparatuses 4(a-d) of the first tofourth cartridges 7(a-d); the toner container portions of the first tofourth cartridges 7 a, 7 b, 7 c, and 7 d contain magenta toner, cyantoner, yellow toner, and black toner, respectively.

The cartridge 7 is made up of the cleaner unit 50 and development unit4A. The cleaner unit 50 comprises the photosensitive drum 1, chargingmeans 2, and cleaning means 6, whereas the development unit 4A comprisesthe developing means for developing an electrostatic latent image on theperipheral surface of the photosensitive drum 1.

The cleaner unit 50 also comprises a frame 51 to which thephotosensitive drum 1, primary charging apparatus 2 for uniformlycharging the photosensitive layer, or the outermost layer, of thephotosensitive drum 1, cleaning blade 60 as the cleaning means 6 forremoving the developer (residual toner) remaining on the peripheralsurface of the photosensitive drum 1 after the image transfer, and aflexible sheet 80, etc., are attached.

The photosensitive drum 1 comprises an aluminum cylinder, and aphotosensitive layer formed on the peripheral surface of the aluminumcylinder. It is provided with flanges 72 and 75, which are attached tothe lengthwise ends of the photosensitive drum 1, one for one. Theflanges 72 and 75 are rotatably supported by supporting members(bearings) 31 a and 31 b, with which the left and right walls of thecleaner unit frame 51 are provided. Of the two flanges 72 and 75, theflange 72 functions as a driving force transmitting member which coupleswith the rotational driving force transmitting member (unshown) of theapparatus main assembly 100, and receives the driving force from thedriving force transmitting member (unshown) of the apparatus mainassembly 100. The configurations of the driving force transmittingmember of the apparatus main assembly 100 and the flange 72, and themanner of their connection, will be described in Section (4).

As the charging apparatus 2, a charging apparatus of a contact type maybe used. The charging member is an electrically conductive roller, theperipheral surface of which is placed in contact with the peripheralsurface of the photosensitive drum 1. The roller is rotated by therotation of the photosensitive drum 1. The peripheral surface of thephotosensitive drum 1 is uniformly charged by applying charge biasvoltage to the roller while the roller is rotated by the rotation of thephotosensitive drum 1.

The residual toner (waste toner) is removed from the peripheral surfaceof the photosensitive drum 1 by the cleaning blade 60, and the removedresidual toner is stored in the waste toner chamber (residual tonerstorage chamber) 55 located above the cleaning blade 60. Incidentally,the toner remaining on the peripheral surface of the photosensitive drum1 after the toner image transfer therefrom moves past the contact areabetween the flexible sheet 80 and the peripheral surface of thephotosensitive drum 1, and reaches the cleaning blade 60. The flexiblesheet 80 is attached to the cleaner unit frame 51 in order to preventthe residual toner from leaking out of the cleaner unit frame 51 afterthe residual toner is removed from the peripheral surface of thephotosensitive drum 1 by the cleaning blade 60.

The development unit 4A comprises: a development sleeve 40, which isrotated (in the direction indicated by arrow mark in FIG. 3), with aminute gap maintained between the peripheral surfaces of the developmentsleeve 40 and photosensitive drum 1 by a pair of spacer rings 40 a; anddevelopment means frames 45 a and 45 b, in which the toner is stored.The developing means frames 45 a and 45 b are joined by ultrasonicwelding or the like means, forming the container unit 46. Thedevelopment sleeve 40 is rotatably supported by the developing meanscontainer unit 46, with a pair of bearings placed between thedevelopment sleeve 40 and the unit 46. In the adjacencies of theperipheral surface of the development sleeve 40, a toner supply roller43, which is rotated in the clockwise direction indicated by an arrowmark in contact with the peripheral surface of the development sleeve40, and the development blade 44, are located. Further, in the tonercontainer portion (developer storage portion) 41 of the developing meanscontainer unit 46, a toner conveyance mechanism 42 for conveying thetoner (unshown) stored in the toner container portion 41, to the tonersupply roller 43 while stirring it, is located.

The development unit 4A is provided with a pair of connective holes 47,which are located at the lengthwise ends of the container unit 46, onefor one, whereas the cleaner unit frame 51 of the cleaner unit 50 isprovided with a pair of supportive holes 52, which are located at thelength ends of the cleaner unit frame 51. The development unit 4A andcleaner unit 50 are connected to each other by inserting a pair of pins49 through the connective holes 47 and supportive holes 52 while holdingthe two units so that the connective holes 47 and supportive holes 52align one for one. As a result. the entirety of the development unit 4Abecomes rotatable about the pins 49, being thereby movable relative tothe cleaner unit 50 while remaining suspended from the cleaner unit 50.Further, the development unit 4A is kept pressured by a pair of springs(unshown) in the direction to rotate the development unit 4A about thepins 49 so that the spacer rings 40 a of the development sleeve 40 arekept in contact with the photosensitive drum 1 in the cleaner unit 50.

During a developing operation, the toner in the toner container 41 isconveyed by the stirring mechanism 42 to the toner supply roller 43,which is being rotated in the clockwise direction, in contact with thedevelopment sleeve 40 which is being rotated also in the clockwisedirection. As a result, the peripheral surface of the supply roller 43is rubbed against the peripheral surface of the development sleeve 40,causing the toner on the peripheral surface of the supply roller 43 tobe transferred onto the peripheral surface of the development sleeve.40.The toner having been borne on the peripheral surface of the developmentsleeve 40 is brought by the rotation of the development sleeve 40 to thedevelopment blade (toner layer regulating member) 44. Thus, as thedevelopment sleeve 40 is further rotated, the layer of the toner on theperipheral surface of the development sleeve 40 is regulated inthickness by the development blade 44, into a thin layer of the toneruniform in thickness, while being given a predetermined amount ofelectric charge. Then, the thin layer of the toner on the peripheralsurface of the development sleeve 40 is brought by the further rotationof the development sleeve 40 to the development station, in which thedistance between the photosensitive drum 1 and development sleeve 40 isextremely small. In the development station, the toner from the thinlayer of the toner on the peripheral surface of the development sleeve40 is adhered to the electrostatic latent image on the peripheralsurface of the photosensitive drum 1, by the development bias applied tothe development sleeve 40 from the electrical power source (unshown); inother words, the latent image is developed. More specifically, thedevelopment sleeve 40 forms (develops) a toner image on the peripheralsurface of the photosensitive drum 1 by transferring toner onto thenumerous points of the electrostatic latent image, which are lower inpotential level.

The toner which did not contribute to the development of the latentimage, that is, the toner which remained on the development sleeve 40,is returned by the further rotation of the development sleeve 40, intothe container unit 46, in which it is stripped from the developmentsleeve 40 by the supply roller 43, in the area in which the peripheralsurfaces of the supply roller 43 and development sleeve 40 are rubbingagainst each other; in other words, the residual toner is recovered intothe container unit 46. The recovered toner is mixed into the toner inthe container unit 46 by the stirring mechanism 42.

Designated by a referential number 54 is a shutter for protecting thephotosensitive drum 1. The shutter 54 is attached to the cleaner unitframe 51. It is movable by a shutter mechanism (unshown) between theclosed position (FIGS. 3-5) in which it covers the photosensitive drumexposure window on the front side of the cartridge 7, and the openposition (indicated by double dot chain line in FIG. 3) into which it ismoved downward from the closed position to expose the photosensitivedrum exposure window. When the cartridge 7 is out of the apparatus mainassembly 100, the shutter 54 is kept in the closed position, protectingthereby the portion of the peripheral surface of the photosensitive drum1, which will remain exposed if there were no the shutter 54. As thefront cover 101 of the apparatus main assembly 100 is closed after themounting of the cartridge 7 into the apparatus main assembly 100, theshutter 54 is moved into the open position by the shutter mechanism(unshown) which is moved by the movement of the front cover 101. As aresult, the electrostatic transfer belt 11 is allowed to be placed incontact with the peripheral surface of the photosensitive drum 1 throughthe aforementioned exposure window of the cartridge 7 (FIG. 1).

Designated by a referential number 53 is a cartridge insertion guide ofthe cleaner unit frame 51. There are two cartridge insertion guides 53located at the left and right lengthwise ends, one for one. Designatedby a referential number 90 is a handle to be used when mounting thecartridge 7 into the apparatus main assembly 100 or removing ittherefrom. There are two handles 90 which project frontward from theleft and right lengthwise ends of the cartridge 7.

(3) Method for Mounting or Removing Cartridge 7

Next, the method for mounting the cartridge 7 into the apparatus mainassembly 100 or dismounting it therefrom will be described. Theoperation for mounting the cartridges 7 into the apparatus main assembly100 or removing them therefrom is to be carried out after opening thefront cover 101 of the apparatus main assembly 100 to fully expose thecartridge insertion opening 91 of the apparatus main assembly 100 (FIGS.2 and 6). When the front cover 101 is in the closed state (FIG. 1), itremains locked to the apparatus main assembly 100 by a latchingmechanism (unshown). Thus, in order to mount or remove the cartridge 7,first, the front cover 101 must be unlocked from the apparatus mainassembly 100 by unlatching the latching mechanism, so that the frontcover 101 can rotated (opened), along with the electrostatictransferring apparatus 5 attached thereto, frontward of the apparatusmain assembly 100, about the hinge shaft 101 a located at the bottom ofthe front cover 101. As the front cover 101 is rotated (opened) all theway, the cartridge insertion opening 91 of the apparatus main assembly100 becomes fully exposed.

Through the cartridge insertion opening 91, the first to fourthcartridges 7 are mountable into the cartridge compartment of theapparatus main assembly 100, in a manner to be stacked in parallel inthe direction slightly tilted from the true vertical direction, in thelisted order, that is, with the first cartridge mounted at the bottom.More specifically, the cartridge compartment is divided into fourcartridge slots, which are the magenta, cyan, yellow, and blackcartridge slots, listing from the bottom. The four cartridge slots areidentical in cartridge mounting mechanism. Each cartridge slot isprovided with a pair of rough guides 103, a pair of middle guides 104,and a pair of guiding grooves 105, for guiding the cartridge 7 into theimage forming position. FIG. 6 shows the inward side of the right plateof the apparatus main assembly 100. The inward side of the left plate issymmetrical with that of the right plate.

An operator is to hold the cartridge 7 by the left and right handles 90,by grasping the handles 90 with both hands, and to insert the cartridge7 into the proper cartridge slot through the cartridge insertion opening91, so that the rear side of the cartridge 7, that is, the side oppositeto the side where the photosensitive drum 1 is exposed, faces forward,and also, so that the left and right lengthwise end portions of thecartridge 7 will be rested on the left and right rough guides 103 of theapparatus main assembly 100, respectively. As the cartridge 7 isinserted deeper into the apparatus main assembly 100, the aforementionedpair of cartridge insertion guides 53 are moved onto the middle guides104, causing thereby the cartridge 7 to be lifted from the rough guides103. Thereafter, the cartridge 7 is guided by the middle guides 104.

As the cartridge 7 is inserted even deeper into the apparatus mainassembly 100, the left and right supporting members 31 a and 31 b of thecartridge 7 are inserted into the left and right guiding grooves 105,respectively. Then, as the cartridge 7 is further inserted, thesupporting members 31 a and 31 b come into contact with the deepest endof the guiding grooves 105, and prevent the further insertion of thecartridge 7 into the apparatus main assembly 100. As a result, thecartridge 7 is precisely positioned relative to the apparatus mainassembly 100 in terms of the widthwise direction.

After the cartridges 7 are inserted into the proper cartridge slots asdescribed above, the front cover 101, which was kept open, is to beclosed, and to be locked to the apparatus main assembly 100 by latchingthe latching mechanism (unshown). The following are accomplished by themeans (unshown) which is moved by the closing movement of the frontcover 101:

-   -   1) Precise positioning of each cartridge 7 relative to the        apparatus main assembly 100 in terms of the widthwise direction        of each cartridge 7, and keeping the cartridge 7 pressured in        the direction in which the cartridge 7 is inserted;    -   2) Moving the shutter 54 of each cartridge 7 into the open        position; and    -   3) Starting the multiple pre-rotations of the image forming        apparatus in order to couple the flange 72, on the driven side,        of the photosensitive drum 1 of each cartridge 7 with the        driving force transmitting member 73 on the main apparatus side.

The function of precisely positioning each cartridge 7 relative to theapparatus main assembly 100 in terms of the widthwise direction of thecartridge 7 is carried out by a pair of pressing members (unshown),which are moved by the movement of the front cover 101. When the frontcover 101 is open, that is, when the front cover 101 is in the state inwhich the cartridges 7 can be mounted into, or removed from, theapparatus main assembly 100, the pressing members are in the positionsinto which they have been retracted from the guiding grooves 105. Thus,when the cartridge 7 is inserted, the pressing members do not interferewith the supporting members 31 a and 31 b of the cartridge 7. However,as the front cover 101 is closed after the insertion of the cartridges7, the pressing members are moved into the positions in which they pressthe supporting members 31 a and 31 b against the deepest end of theguiding grooves 105, precisely positioning thereby the cartridge 7relative to the apparatus main assembly 100 in terms of the widthwisedirection.

With each cartridge 7 precisely positioned relative to the apparatusmain assembly 100, the flange 72, on the driven side, of the cartridge7, and the driving force transmitting rotational member 73 of theapparatus main assembly 100 become coupled with each other, making itpossible for the diving force from the motor (unshown) of the apparatusmain assembly 100 to be transmitted to the flange 72, on the drivenside, of the cartridge 7, through the driving force transmittingrotational member 73; in other words, it becomes possible for thephotosensitive drum 1 of each cartridge 7 to be rotationally driven. Itshould be noted here that the development sleeve 40, toner conveyancemechanism 42, and toner supply roller 43 are driven by the rotation ofthe photosensitive drum 1 through the gear train (unshown).

Also, electrical connection is established between the electricalcontacts (unshown) on the cartridge side and the electrical contacts(unshown) on the main assembly side, making it possible for charge biasand development bias to be applied to the cartridge 7 from the powersource (unshown) of the apparatus main assembly 100, and also, forinformation or the like to be exchanged between the memory element onthe cartridge side and the control circuit on the apparatus mainassembly side. The structure for grounding the photosensitive drum 1will be described later in Section (4).

All that is necessary to remove the cartridge 7 from the apparatus mainassembly 100 is to carry out in reverse the above described steps formounting the cartridge into the apparatus main assembly 100. That is,first, the aforementioned latching mechanism is to be unlatched tounlock the front cover 101 from the apparatus main assembly 100. Thenthe front cover 101 is rotated downward about the hinge shaft 101 alocated at the bottom of the front cover 101 in order to open the frontcover 101 frontward. As the front cover 101 is rotated downward, thecartridge pressing members are retracted by the means which moved by theopening movement of the front cover 101, being stopped from pressing thecartridge 7. Also as the front cover 101 is opened, the driving forcetransmitting rotational member 73 becomes disengaged from the flange 72of the driven side, and the shutter 54 is moved into the open position.Then, an operator is to grasp the handles 90 of the cartridge 7 withboth hands, and to pull the cartridge 7 in the direction opposite to thedirection in which the cartridge 7 is pushed when it is mounted into theapparatus main assembly 100. This will remove the cartridge 7 from theapparatus main assembly 100.

(4) Method for Connecting Drum Grounding Plate 71)

Next, referring to FIGS. 7-10, the method for connecting the drumgrounding plate 71 attached to the flange 72 on the driven side will bedescribed in more detail.

FIG. 7 is a perspective view of the photosensitive drum (whichhereinafter will be referred to as photosensitive drum unit) 1, and thedriving force transmitting rotational member 73 on the apparatus mainassembly side. FIG. 8 is a combination of a perspective view andvertical sectional views of the photosensitive drum unit 1, showing thesteps followed to assemble the photosensitive drum unit 1. FIGS. 9 and10 are enlarged views of the E portion in FIG. 8, showing the state ofconnection between the drum grounding plate 71 and drive shaft 70. FIG.9 shows the positional relationship between the drum grounding plate 71and drive shaft 70 at the moment the two have just come into contactwith each other, or immediately before the two become separated fromeach other. FIG. 10 shows the positional relationship between the drumgrounding plate 71 and drive shaft 70 when the cartridge 7 has beensuccessfully mounted, being therefore ready for image formation.

First, referring to FIG. 7, the structure of the photosensitive drumunit 1 will be described.

The photosensitive drum unit 1 has a drum cylinder 74, which comprises,as described before, an aluminum cylinder and a layer of photosensitivesubstance coated on the peripheral surface of the aluminum cylinder. Thephotosensitive drum unit 1 also has a pair of flanges 72 and 75, whichare pressed into the openings of the lengthwise ends of the drumcylinder 74, being virtually integrated with the drum cylinder 74. Theflanges 72 and 75 are rotatably supported by the bearing members 31 aand 31 b (FIGS. 4 and 5) with which the cartridge 7 is provided. To theflange 72 located at one of the lengthwise ends of the photosensitivedrum unit 1, the driving force is transmitted from the motor (unshown)within the apparatus main assembly 100 through the driving forcetransmitting rotational member 73, rotating thereby the photosensitivedrum unit 1. In this embodiment, hereinafter, the flange 72 to which thedriving force is transmitted from the apparatus main assembly 100 willbe referred to as the driver flange 72, whereas the other flange will bereferred to as the non-driver flange 75.

FIG. 9 is an enlarged view of the joint between the driver flange 72 anddriving force transmitting rotational member 73. The driver flange 72 isprovided with a spiral projection 72 a (coupling projection) with anon-circular cross section; the cross section of the spiral projectionhas a plurality of apexes. The apparatus main assembly 100 is providedwith the driving force transmitting rotational member 73 fortransmitting the driving force from the motor (unshown) within theapparatus main assembly 100, to the photosensitive drum unit 1. Thedriving force transmitting rotational member 73 has a spiral hole 73 a(coupling hole) with a non-circular cross section; the cross section ofthe spiral hole has a plurality of apexes. The axial line of the spiralhole 73 a coincides with that of the driving force transmittingrotational member 73. As the cartridge 7 is mounted into the apparatusmain assembly 100, the spiral projection 72 a enters the spiral hole 73a, enabling the rotational driving force to be transmitted to thephotosensitive drum unit 1. As the driving force transmitting rotationalmember 73 is rotated by the motor on the apparatus main assembly side, aforce A′ which acts in a direction to pull the spiral projection 72 ainto the spiral hole 73 is generated, causing the driving forcetransmitting rotational member 73 and the photosensitive drum unit 1 tobe drawn toward each other.

The spiral projection 72 a is provided with an electrically conductivesecond member 71 (which hereinafter will be referred to as a drumgrounding plate) for establishing an electrical connection between thephotosensitive drum unit 1 and apparatus main assembly 100. The drumgrounding plate 71 is located at the center of the spiral projection 72a, in terms of the radius direction of the projection 72 a, and isplaced in contact with the internal surface of the drum cylinder 74. Thedriving force transmitting rotational member 73 is provided with anelectrically conductive first member 70 (which hereinafter will bereferred to as a drive shaft) for establishing our electrical connectionbetween the photosensitive drum unit 1 and apparatus main assembly 100.The electrically conductive first member, or the drive shaft 70,projects a predetermined distance from the center of the bottom of thespiral hole 73 a. The first and second electrically conductive members70 and 71 allow the residual electric charge of the photosensitive drumunit 1 to escape to the apparatus main assembly 100.

Referring to FIG. 8, the drum grounding plate 71 is a single-piecemember, and flat contact portion 71 a, and a contact portion 71 b in theform of an arm. The flat contact portion 71 a, as one of the contactingmeans, is supported by the flat portion 72 g provided within the driverflange 72. The arm-shaped contact portion 71 b as the other contactingmeans is formed by bending or the like method. In terms of thelengthwise direction, the arm-like contact portion 71 b extends outwardbeyond the flat contact portion 71 a.

Referring to FIG. 9, the driver shaft 70, which is on the apparatus mainassembly side, rotates with the driving force transmitting rotationalmember 73. The driver flange 72 is provided with a hole 72 j into whichthe drive shaft 70 fits, and which is located roughly at the center ofthe driver flange 72 in terms of the radius direction. When the imageforming apparatus is actually ready for image formation, the tip 70 a ofthe drive shaft 70 is in contact with the flat contact portion 71 a. Theflat contact portion 71 a is supported (backed) by the flat portion 72 gprovided within the driver flange 72. As the drive force transmittingrotational member 73 is rotated, with the spiral projection 72 a beingin the spiral hole 73 a, the force A′ which acts in the direction topull the projection 72 a into the hole 73 a is generated. The contactpressure generated by the force A′ applies to the tip 70 a of the driveshaft 70 and the flat contact portion 71 a. This concludes the couplingbetween the driving force transmitting rotational member 73 and driverflange 72 (photosensitive drum unit 1). The driving force transmittingrotational member 73 is provided with a spring (unshown) for keeping theconnected photosensitive drum unit 1 pressured in the lengthwisedirection. Thus, the non-driver flange 75 is kept pressured upon thecleaner unit 50 (cartridge 7) through the photosensitive drum unit 1.Therefore, the cleaner unit 50 is kept pressed upon-the side plate 102of the apparatus main assembly 100. As a result, the cartridge 7 isprecisely positioned-relative to the apparatus main assembly 100 interms of the lengthwise direction.

Next, the process through which the drum grounding plate 71 becomesconnected to its counterpart will be described in detail. Referring toFIG. 9 which shows the positional relationship between the drumgrounding plate 71 and drive shaft 70 at the moment the two have justcome into contact with each other, or immediately before the two becomeseparated from each other, prior to the insertion of the cartridge 7into the apparatus main assembly 100, the driving force transmittingrotational member 73 of the apparatus main assembly 100 remainsretracted, being thereby prevented from interfering with the insertionof the cartridge 7. As the cartridge 7 is mounted into the apparatusmain assembly 100, and the front cover 101 of the apparatus mainassembly 100 is closed (FIG. 2), the driving force transmittingrotational member 73.is moved, while being rotated, toward the driverflange 72 in the lengthwise direction. As a result, the cartridge 7(driver flange 72) and the apparatus main assembly 100 (driving forcetransmitting rotational member 73) become partially connected; thespiral projection 72 a partially enters the spiral hole 73 a.

In this state, the pre-rotation step (in which the apparatus is drivenfor a predetermined length of time between when a print start signal isinputted and when an actual image forming operation starts) is carriedout. During this pre-rotation step, a rotational driving force isinputted from the driving force transmitting rotational member 73 intothe drive flange 72 integral with the photosensitive drum unit 1. Thereoccurs sometimes that the spiral projection 72 a fails to enter thespiral hole 73 a (the driver flange 72 fails to mesh with the drivingforce transmitting rotational member 73) because they fail tosynchronize in rotational phase during the preceding step, that is, theclosing of the front cover 101 of the apparatus main assembly 100.However, the driving force transmitting rotational member 73 is keptpressed upon 20 the photosensitive drum unit 1 (driver flange 72) in thelengthwise direction, as described above. Therefore, the driver flange72 and the driving force transmitting rotational member 73 areeventually made to synchronize in rotational phase, meshing thereforewith each other, during this pre-rotation period.

As the rotational driving force is inputted, with the driving forcetransmitting rotational member 73 and the driver flange 73 partiallymeshed (the spiral projection 72 a being partially placed in the spiralhole 73 a), the force A′, which acts in the direction to draw thedriving force transmitting rotational member 73 and driver flange 72(photosensitive drum unit 1) toward each other (draw spiral projection72 a into spiral hole 73 a), is generated. As a result, the spiralprojection 72 a is drawn into the spiral hole 73 a. Therefore, in thedriver flange 72, the drive shaft 70 and drum grounding plate 71 aredrawn toward each other, causing the tip of the arm-shaped contactportion 71 b of the drum grounding plate 71 to come into contact withthe tip of the drive shaft 70, at a point b1 (FIG. 9).

As the input of the rotational driving force is continued, thegeneration of the force A′ also continues, causing the tip of thearm-shaped contact portion 71 b of the drum grounding plate 71 to followthe surface of the tip 70 b of the drive shaft 70 in the radiusdirection of the drive shaft 70 as indicated by a referential letter c.In other words, the contact point between the tip of the arm-shapedportion 71 b of the drum grounding plate 71 and drive shaft 70 shifts asthe spiral projection 72 a is drawn into the spiral hole 73 a. Since thedrum grounding plate 71 is formed of an electrically conductive elasticsubstance, it elastically deforms. Therefore, the tip in the arm-shapedportion 71 b of the drum grounding plate 71 slides on the surface of thetip 70 b of the drive shaft 70, while applying a slight pressure uponthe surface of the tip 70 b of the drive shaft 70, while the spiralprojection 72 a is drawn into the spiral hole 73 a.

In other words, as the input of the rotational driving force continues,the spiral projection 72 a is drawn into the spiral hole 73 a so thatthe drive shaft 70 and drum grounding plate 71 are drawn to each other.As a result, the tip 70 a of the drive shaft 70 comes into contact withthe flat portion 71 a of the drum grounding plate 71 as shown in FIG.10. In other words, at the same time as the cartridge 7 is preciselypositioned relative to the apparatus main assembly 100, electricalconnection is established between the apparatus main assembly 100 andpresent invention drum unit 1 by the contact pressure A′, which is thecombination of the force A and the pressure generated by the resiliencyof the springs (unshown). Until the tip 70 a of the drive shaft 70, andthe flat portion 71 a of the drum grounding plate 71 come into contactwith each other, the drive shaft 70 is continuously rotated relative tothe drum grounding plate 71. Thus, during this period, the tip of thearm-shaped portion 71 b keeps on sliding on the surface of the tip 70 bof the drive shaft 70, not only in the lengthwise direction of the driveshaft 70, but also, in the radially outward direction of the drive shaft70. In other words, the tip of the arm-shaped portion 71 b of the drumgrounding plate 71 slides on the surface of the tip of the shaft 70,from the contact point b1 (FIG. 9) to the contact point b2 (FIG. 10) asindicated by the referential letter c in FIGS. 9 and 10. Thereafter, theelectrical connection between the apparatus main assembly 100 andphotosensitive drum unit 1 is maintained at the contact point b2 betweenthe tip of the arm-shaped portion 71 b of the drum grounding plate 71,and the surface of the tip 70 a of the shaft 70, by the contact pressureB generated by the arm-shaped portion 71 b of the drum grounding plate71.

With the employment of the above-described method for electricallyconnecting the drum grounding plate 71 to the drive shaft 70, thecontact point between the photosensitive drum unit 1 and the drive shaft70 does not shift (slide) in the lengthwise direction during the actualimage forming operation. That is, while the driver flange 72 and thedriving force transmitting rotational member 73 are rotating together,with the spiral projection 72 a engaged in the spiral hole 73 a, thedrum grounding plate 71 (flat portion 71 a and arm-shaped portion 71 b)and the drive shaft 70 (tip 70 a of drive shaft) rotate together whileremaining in contact with each other. Therefore, the cartridge 7 isreliably grounded to the apparatus main assembly 100. The drive shaft70, which rotates with the driving force transmitting rotational member73, is connected to the power supplying member (unshown) of theapparatus main assembly 100. The portion of the drive shaft 70 (portionof the power supplying member), which rubs against the power supplyingmember is coated with electrically conductive grease to assure that thecartridge 7 is grounded to the apparatus main assembly 100. It should benoted here that the contact point between the photosensitive drum unit 1and drive shaft 70, which a user can touch, is not coated withelectrically conductive grease. With the provision of theabove-described structural arrangement in this embodiment of the presentinvention in which the contact point between the apparatus main assembly100 and the cartridge 7 does not shift in the lengthwise directionduring a period in which an image is actually formed, the cartridge 7remains better grounded than with the provision of the structuralarrangement in accordance with the prior art. Further, while the driverflange 72 (drum grounding plate 71) and the drive shaft 70 rotatetogether, with the spiral projection 72 a remaining in the spiral hole73 a, the wall of the hole 72 j into which the drive shaft 70 fits, anddrum grounding plate 71, are prevented from being worn by the frictionbetween the two, minimizing therefore their frictional wear.

The contact pressure between the flat portion 71 a of the drum groundingplate 71 and the tip 70 a of the drive shaft 70 is generated by theforce A′ generated as the drive shaft 70 is rotated by the rotationaldriving force transmitted thereto. In other words, the contact pressureis generated only while the driving force is inputted. Therefore, themembers pertinent to the electrical connection between the apparatusmain assembly 100 and cartridge 7 are less likely to suffer fromfatigue. In addition, at the beginning of the transmission of thedriving force, the contact point between the tip 70 a of the drive shaft70 and the flat portion 71 a of the drum grounding plate 71 slightlyshifts, creating the wiping effect.

As for the grounding of the photosensitive drum unit 1 through thearm-shaped portion 71 b, or the other contact point, of the drumgrounding plate 71, as the spiral projection 72 a is drawn into thespiral hole 73 a, the tip of the arm-shaped portion 71 b slides on thesurface of the tip 70 b of the drive shaft 70 while being kept incontact with the surface by its own resiliency. In other words, it wipesitself while wiping the surface of the tip 70 b of the shaft 70, bettergrounding therefore the photosensitive drum unit 1.

The configuration of the tip (inclusive of points 70 a and 70 b) of thedrive shaft 70 does not need to be limited to the one in thisembodiment. It has only to be such that allows the tip of the arm-shapedportion 71 b of the drum grounding member 71 to be slid on the surfaceof the tip (inclusive of points 70 a and 70 b) of the shaft 70 as thespiral projection 72 a is drawn into the spiral hole 73 a.

Referring to FIGS. 9 and 10, in this embodiment, the arm-shaped portion71 b of the drum grounding plate 71 is shaped so that while its tipslides on the surface of the tip 70 a of the drive shaft 70, the angleof the surface of the tip of the arm-shaped portion 71 b relative to theline tangential to the surface of the tip 70 b of the drive shaft 70remains as small as possible, making it easier for the tip of thearm-shaped portion 71 a to slide on the surface of the tip 70 a of thedrive shaft 70. Obviously, as long as the arm-shaped portion 71 b isshaped so that as the spiral projection 72 a is drawn into the spiralhole 73 a, the tip of the arm-shape portion 71 b is allowed to slide on(move in contact with) the surface of the tip 70 a of the drive shaft70, the same wiping effect as that realized by this embodiment can berealized. In other words, the arm-shaped portion 71 b of the drumgrounding plate 71 may be differently bent from the shape in which it isbent in this embodiment.

Further, in this embodiment, the arm-shaped portion 71 b and flatportion plate 71 b of the drum grounding plate 71 are formed by cuttingand bending a single piece of an electrically conductive springy plate.However, the same effects as those described above can be obtained evenif two or more electrically conductive members are combined to form thedrum grounding plate 71 having the flat and arm-shaped portions 71 a and71 b. Further, even if the spiral hole 73 a with a non-circular crosssection and spiral projection 72 a with a non-circular cross section areswitched in position, the same effects as those obtained by thisembodiment can be obtained. In other words, even if the driver flange 72is provided with a non-circular spiral hole 73 a which has a crosssection having a plurality of apexes, and the rotational axis of whichcoincides with that of the flange 72, and the driving force transmittingrotational member 73 of the apparatus main assembly 100 is provided witha spiral projection (72 a) which has a cross section having a pluralityof apexes, and the rotational axis of which coincides with that of thedriving force transmitting rotational member 73, the same effects asthose obtained by this embodiment can be obtained.

Further, the drive shaft 70 and drum grounding plate 71 may be switchedin position. In other words, even if the drum grounding plate 71 ispositioned at the center of the spiral hole 73 a with a non-circularcross section, and the spiral projection 72 a with a non-circular crosssection is provided with the drive shaft 70, the rotational axis ofwhich coincides with that of the spiral projection 72 a, the sameeffects as those obtained by this embodiment can be obtained. However,placing the drum grounding plate 71 at the center of the spiralprojection 72 a with a non-circular cross section makes the hole 72 j ofthe spiral projection 72 a, through which the drive shaft 70 is put tobe connected to the drum grounding plate 71, identical in diameter asthe drive shaft 70, and therefore, making it possible to reduce thespiral hole 73 a in cross section. Therefore, placing the drum groundingplate 71 at the center of the spiral projection 72 a is superior for thepurpose of preventing foreign objects from coming into contact with thespringy drum grounding plate 71 from outside.

(5) Attachment of Drum Grounding Plate 71

Next, referring to FIG. 8, the steps to be followed in order to attachthe drum grounding plate 71 to the driver flange 72 will be described indetail.

FIG. 8 is a combination of a perspective view and vertical sectionalviews of the driver flange 72 and drum grounding plate 71, showing thesteps to be followed to attach the drum grounding plate 71.

The drum grounding plate 71 is attached to the driver flange 72following steps 1)-8) in the numerical order. FIG. 8 (step 1) shows thedrum grounding plate 71 and driver flange 72 prior to the attachment ofthe drum grounding plate 71 to the driver flange 72.

The drum grounding plate 71 in this embodiment is bent roughly in theshape of a letter L. In the sectional view of the drum grounding plate71, at a plane perpendicular to the vertical portion of the letter “L”(direction perpendicular to lengthwise direction described before), thedrum grounding plate 71 has a pair of projections 71 c (by which drumgrounding plate 71 is guided), which perpendicularly project from thelongest edges of the drum grounding plate 71, one for one. The drumgrounding plate 71 also has: a positioning hole 71 d for preciselypositioning the drum grounding plate 71 within the driver flange 72; aprojection 71 e by which the drum grounding plate 71 is placed incontact with the internal surface of the drum cylinder to establishelectrical connection between the drum grounding plate 71 and the drumcylinder 74; and aforementioned flat and arm-shaped portion 71 a and 71b.

The driver flange 72 is provided with a positioning pin 72 b which fitsinto the positioning hole 71 d of the drum grounding plate 71, and thespiral projection 72 a (coupling portion) with a non-circular crosssection, which has a plurality of apexes and projects from the end ofthe driver flange 72. Referring to FIG. 8 (step 2), the driver flange 72is provided with an internal space 72 c into which the drum groundingplate 71 is inserted. When attaching the drum grounding plate 71 to thedriver flange 72, the drum grounding plate 71 is to be inserted, fromits contact point side, into the driver flange 72 from the rear end ofthe driver flange 72 toward the front end, provided that the portion ofthe driver flange 72, which has the coupling portion, is the front endportion.

As the drum grounding plate 71 is inserted further into the driverflange 72 as shown in FIG. 8 (step 3), the pair of projections 71 c,which perpendicularly project from the longest edges of the drumgrounding plate 71, come into contact with a pair guide portions 72 d ofthe driver flange 72, which are located within the internal space 72 c.Each guide portion 72 d is tilted backward in terms of the direction inwhich the drum grounding plate 71 is inserted into the drum groundingplate 71; in other words, the bottom end of the guide portion 72 d islocated more inward of the internal space 72 c than the top end of theguide portion 72 d. Therefore, as the drum grounding plate 71 is furtherinserted, it is guided downward in the drawing by the pair of guidingportions 72 d. As a result, the tip portion of the drum grounding plate71, which essentially is the contact point, is elastically deformed intothe space 72 c, and the positioning pin 72 b of the driver flange 72,which projects from the rear surface of the driver flange 72 fits intothe positioning hole 71 d of the drum grounding plate 71.

The bottom end of each of the slanted guide portion 72 d is connected tothe slit (groove) 72 e, the dimension of which in terms of the verticaldirection in FIG. 8 is equal to the thickness of the drum groundingplate 71. Thus, as the drum grounding plate 71 is further insert afterits contact with the pair of guiding portions 72 d in FIG. 8 (step 4),the pair of projections 71 c of the drum grounding plate 71 slide intothe pair of slits (grooves) 72 e, one for one. Even after the sliding ofthe pair of projections 71 c of the drum grounding plate 71 into thepair of slits (grooves) 72 e, the tip portion of the drum groundingplate 71 is kept within the space 72 c by the resiliency of the drumgrounding plate 71.

The leading end portion of the drum grounding plate 71, in terms of theplate insertion direction, is provided with a catch portion 71 f formedby bending the very tip of the leading end portion of the drum groundingplate 71. Thus, as the drum grounding plate 71 is further inserted intothe driver flange 72 while elastically bending the trailing end portionof the drum grounding plate 71 in the direction indicated by an arrowmark in FIG. 8 (step 4), the catch portion 71 f is moved beyond the flatend portion 72 g of the driver flange 72, and is moved downward, in thedrawing, sliding on the flat end portion 72 g, by the resiliency of thedrum grounding plate 71 itself. In other words, the tip of the drumgrounding plate 71 is moved downward in the space 72 c, as shown in FIG.8 (step 5).

Further, the driver flange 72 is provided with a recess 72 f into whichthe catch portion 71 f of the drum grounding plate 71 latches. As thepressure applied to the rear end of the drum grounding plate 71 isremoved, the resiliency of the drum grounding plate 71 generates suchforce that acts in the direction to move the tip of the drum groundingplate 71 in the direction indicated by an arrow mark in FIG. 8 (step 6).As a result, the back side of the flat portion 71 a of the drumgrounding plate 71 is placed flatly in contact with the flat portion 72g of the driver flange 72. It should be noted here that the dimension m(distance between the rear end and flat end portion 72 g of the driverflange 72) and dimension n (distance between the rear end and flatportion 71 a of the drum ground plate 71) are set so that even if thecombination of the tolerances of the drum grounding plate 71 and riverflange 72 is substantial, the equation n=m is satisfied, ensuring thatthe flat portion 71 a of the drum grounding plate 71 is placed flatly incontact with the flat end portion 72 g of the driver flange 72.

The catch portion 71 f located at the very tip of the drum groundingplate 71 latches into the recess 72 f of the driver flange 72,preventing thereby the drum grounding plate 71 from floating upward,since the catch portion 71 f is formed by bending rearward the very tipof the drum grounding plate 71. Therefore, it entirely fits into therecess 72 f of the driver flange 72, and therefore, does not interferewith the electrical connection between the drum grounding plate 71 anddrive shaft 70.

In the step 7), the positioning pin 72 b is thermally deformed to form aretainer portion 72 h in order to prevent the drum grounding plate 71from moving relative to the driver flange 72.

The above described steps 1)-7) ensure that the drum grounding plate 71is precisely positioned in the driver flange 72. In particular, theyensure that the aforementioned two contact points between the driveshaft 70 and drum grounding plate 71 remain stable in position.

In the step 8), or the last step, the rear end portion 72 i of thedriver flange 72 is pressed into the drum cylinder 74. During this step,the projection 71 e of the drum grounding plate 71 slides on theinternal surface of the drum cylinder 74. After the rear portion 72 i ofthe drum grounding plate 71 is pressed into the drum cylinder 74, theprojection 71 e is kept pressed upon the internal surface of the drumcylinder 74 by the resiliency of the drum grounding plate 71, ensuringthe electrical connection between the drum grounding plate 71 and drumcylinder 74.

The above described steps for assembling the photosensitive drum unit 1makes it possible to work on the driver flange 72, from one end of thedriver flange 72, that is, the drum grounding plate 71 can be simplyinserted into the driver flange 72, from the rear end of the driverflange 72, improving the efficiency with which the photosensitive drumunit 1 is assembled. Further, since the drum grounding plate 71 isformed as a single-piece component, and the interior of the driverflange 72 is structured as described above, not only is it ensured thatthe photosensitive drum unit 1 is properly grounded, but also, thephotosensitive drum unit 1 is improved in assembly efficiency. In otherwords, according to this embodiment of the present invention, the drumunit 1 can be reliably grounded to the apparatus main assembly 100 withthe use of the simpler structural arrangement, improving thereby theimage forming apparatus in cost performance.

As described above, in this embodiment:

1) The photosensitive drum unit 1 is grounded through the electricalconnection between the drive shaft 70 (first conductive member) on themain assembly side of the image forming apparatus, and the drumgrounding plate 71 (second conductive member) placed within the drumcylinder 74 of the photosensitive drum unit 1. In the case of thisstructural arrangement, the drum grounding plate 71 is provided with theflat contact portion 71 a and arm-shaped contact portion 71 b. and asthe rotational driving force is transmitted to the spiral projection 72a having entered the spiral hole 73 a, the force A′ which draws thespiral projection 72 a into the spiral I hole 73 a (driving forcetransmitting rotational member 73) is generated, causing thephotosensitive drum unit 1 to be moved toward the driving forcetransmitting rotational member 73. Then, as the photosensitive drumunit.1 is moved toward the driving force transmitting rotational member73, the flat contact portion 71 a of the drum grounding plate 71 comesinto contact with the tip of the drive shaft 70, and the tip of thearm-shaped portion 71 b slides on the surface of the tip 70 a of thedrive shaft 70. In other words, the structural arrangement in thisembodiment provides two means for electrically connecting thephotosensitive drum unit 1 and apparatus main assembly 100, making itpossible to better grounding the photosensitive drum unit 1.

Further, the contact point of the photosensitive drum unit 1 and thecontact point of the drive shaft 70 are prevented from keeping onrubbing each other after they are connected, making it possible for thecartridge 7 to be more reliably grounded to the apparatus main assembly100. Further, the drive flange 72 (drum grounding plate 71) is solidlylocated with the drive shaft 70. Therefore, the wall of the hole 72 j ofthe driver flange 72, into which the drive shaft 70 fits, and the drumgrounding plate 71, are presented from being frictionally worn.

As for the first means for electrically connecting the photosensitivedrum unit 1 to the apparatus main assembly 100, the flat contact portion71 a of the drum grounding plate 71 is placed, and kept, in contact withthe tip 70 a of the drive shaft 70 by the contact pressure, or the forceA′ generated in the direction to draw the spiral projection 72 a of thedriver flange 72 into the spiral hole 73 a of the driving forcetransmitting rotational member 73 as the rotational driving force istransmitted to the spiral projection 72 a placed in the spiral hole 73a. Therefore, the contact pressure applies only while the driving forceis inputted, preventing the components pertinent to the electricalconnection between the photosensitive drum unit 1 and apparatus mainassembly 100 from being fatigued by the contact pressure. Further, thepoint of contact between the contact points on the photosensitive drumunit side and the contact point on the apparatus main assembly side arestructured so that they slightly shift in position, and once theconnection is fully established, they do not shift in position while thedriving force is transmitted. Therefore, the tip 70 a of the drive shaft70 and the flat contact portion 71 a of the drum grounding plate 71 wipeeach other at the beginning of the transmission of the driving force,and yet, the components pertinent to the electrical connection betweenthe photosensitive drum unit 1 and apparatus main assembly 100 are notfrictionally worn during the rest of the transmission of the drivingforce.

As for the second means for electrically connecting the photosensitivedrum unit 1 to the apparatus main assembly 100, the arm-shaped portion71 b of the drum grounding plate 71 slides on the surface of the tip 70b of the drive-shaft 70, while being kept pressured upon the surface ofthe end portion 70 b of the drive shaft 70 by the resiliency of the drumgrounding plate 71. Therefore, the point of contact between thearm-shaped portion 71 b and tip 70 b shifts in position only at thebeginning and end of the transmission of the driving force; it does notshift in position during the rest of the driving force transmission.Therefore, the arm-shaped portion 71 b and the tip 70 b of the driveshaft 70 wipe each other as they become fully connected, ensuring theelectrical connection between the photosensitive drum unit 1 andapparatus main assembly 100.

2) The drum grounding plate 71 having the flat contact portion 71 a andthe arm-shaped contact portion 71 b is formed as a single-piececomponent, reducing thereby the component count.

3) As the means for accurately attaching the drum grounding plate 71 tothe driver flange 72, the driver flange 72 is provided with the pair ofguide portions 72 d for guiding the drum grounding plate 71 to thepredetermined position in the internal space 72 c, whereas the drumgrounding plate 71 is provided with the pair of projections 71 c bywhich the drum grounding plate 71 is guided by the pair of guideportions 72 d. Therefore, the drum grounding plate 71 can be attached tothe driver flange 72 by simply pushing the drum grounding plate 71 intothe driver flange 72 from the rear end of the driver flange 72,improving the photosensitive drum unit 1 in assembly efficiency.

4) For the purpose of preventing the drum grounding plate 71 from movingafter its attachment to the driver flange 72, the drum grounding plate71 is provided with the catch portion 71 f bent toward the rear of thedrum grounding plate 71, whereas the driver flange 72 is provided withthe recess 71 f into which the catch portion 71 f latches. In addition,the drum grounding plate 71 is shaped so that as the drum groundingplate 71 is attached to the driver flange 72, the catch portion 71 flatches into the recess 72 f and remains latched therein, by theresiliency of the drum grounding plate 71 itself. Therefore, the actualcontact portion, or the tip, of the drum grounding plate 71 is preventedfrom floating (becoming separated) from the driver flange 72. Therefore,it is assured that the point of contact is precisely position.Consequently, the photosensitive drum unit 1 is better grounded.

5) The photosensitive drum unit 1 having the above described drumgrounding features 1)-4) may be structured so that it can be directlymounted into, or removed from, the apparatus main assembly 1000, withoutbeing placed in the process cartridge. Such an arrangement also producesthe same effects as those described above.

[Miscellanies]

1) As for the developing method, one of the widely known developingmethods, for example, two component magnetic brush based developingmethod, cascade developing method, touch-down developing method, clouddeveloping method, etc., may be employed, instead of the developingmethod employed in the above described embodiment.

2) In the above described embodiment, the so-called contact typecharging method is employed as the charging means. Obviously, thecharging method does not need to be limited to the above described one.For example, one of the charging methods, which has been widely used inthe past, may be employed. Namely, a piece of tungsten wire issurrounded on three sides by a shield formed of metallic substance suchas aluminum, so that the positive or negative ions generated by applyinghigh voltage to the tungsten wire can be transferred onto the peripheralsurface of the photosensitive drum in order to uniformly charge theperipheral surface of the photosensitive drum.

As for the charging means, a blade (charge blade), a pad, a block, arod, a wire, or the like, may be employed in stead of the aforementionedroller.

3) As for the method for removing the toner remaining on thephotosensitive drum, a cleaning means in the form of a blade, a furbrush, a magnetic brush, or the like, may be employed instead of theabove described one.

According to the present invention, it is possible to provide anelectrophotographic photosensitive drum capable of reliably establishingelectrical connection between it and the main assembly of anelectrophotographic image forming apparatus, a process cartridgecomprising said electrophotographic photosensitive drum, and anelectrophotographic image forming apparatus compatible with saidelectrophotographic photosensitive drum and process cartridge.

Also according to the present invention, it is possible to provide anelectrophotographic photosensitive drum capable of wiping itselectrically conductive member in order to be reliably grounded, aprocess cartridge comprising the electrophotographic photosensitivedrum, and an electrophotographic image forming apparatus compatible withthe electrophotographic photosensitive drum and process cartridge.

Also according to the present invention, it is possible to provide anelectrophotographic photosensitive drum capable of rotating the firstand second electrically conductive members together in order to preventthe conductive members from being frictionally worn, a process cartridgecomprising the electrophotographic photosensitive drum, and anelectrophotographic image forming apparatus compatible with theelectrophotographic photosensitive drum and the process cartridge.

While the invention has been described with reference to the structuresdisclosed herein, it is not confined to the details set forth, and thisapplication is intended to cover such modifications or changes as maycome within the purposes of the improvements or the scope of thefollowing claims.

This application claims priority from Japanese Patent Application No.099503/2004 filed Mar. 30, 2004, which is hereby incorporated byreference.

1. An electrophotographic photosensitive drum usable with anelectrophotographic image forming apparatus, comprising: a non-circulartwisted projection having a cross-section with a plurality of cornerportions, said non-circular twisted projection being provided at onelongitudinal end of said electrophotographic photosensitive drum, andbeing engageable with a non-circular twisted hole having a cross-sectionwith a plurality of corner portions, the non-circular twisted hole beingdisposed at a central portion of a driving rotatable member of a mainassembly of the image forming apparatus; and a drum electroconductivemember provided on said projection and being electrically connected withsaid electrophotographic photosensitive drum, said drumelectroconductive member being contactable with a main-assemblyelectroconductive member electrically connected with the main assemblyof the image forming apparatus, the main-assembly electroconductivemember being disposed in the hole to ground said electrophotographicphotosensitive drum, wherein a contact position between said drumelectroconductive member and the main-assembly electroconductive membermoves in interrelation with said projection being moved toward the holeby rotation of the driving rotatable member when said projection isengaged with the hole of the driving rotatable member.
 2. Anelectrophotographic photosensitive drum usable with anelectrophotographic image forming apparatus, comprising: a non-circulartwisted projection having a cross-section with a plurality of cornerportions, said non-circular twisted projection being provided at onelongitudinal end of said electrophotographic photosensitive drum, andbeing engageable with a non-circular twisted hole having a cross-sectionwith a plurality of corner portions, the non-circular twisted hole beingdisposed at a central portion of a driving rotatable member of a mainassembly of the image forming apparatus; and a drum electroconductivemember provided on said projection and being electrically connected withsaid electrophotographic photosensitive drum, said drumelectroconductive member being contactable with a main-assemblyelectroconductive member electrically connected with the main assemblyof the image forming apparatus, the main-assembly electroconductivemember being disposed in the hole to ground said electrophotographicphotosensitive drum, wherein while said projection is in engagement withthe hole and is being rotated, said main-assembly electroconductivemember and said drum electroconductive member are integrally rotatedwhile being in contact with each other.
 3. An electrophotographicphotosensitive drum according to claim 1 or 2, wherein said drumelectroconductive member is one member.
 4. An electrophotographicphotosensitive drum according to claim 1 or 2, wherein a driving sideflange member of said non-circular twisted projection has a guideconfigured and positioned to urge said drum electroconductive member toa predetermined position when said drum electroconductive member ismounted to said driving side flange member, and said drumelectroconductive member has an engaging portion configured andpositioned to engage said guide.
 5. A process cartridge detachablymountable to an electrophotographic image forming apparatus, saidprocess cartridge comprising: an electrophotographic photosensitivedrum; a non-circular twisted projection having a cross-section with aplurality of corner portions, said non-circular twisted projection beingprovided at one longitudinal end of said electrophotographicphotosensitive drum, and being engageable with a non-circular twistedhole having a cross-section with a plurality of corner portions, thenon-circular twisted hole being disposed at a central portion of adriving rotatable member of a main assembly of the image formingapparatus; and a drum electroconductive member provided on saidprojection and being electrically connected with saidelectrophotographic photosensitive drum, said drum electroconductivemember being contactable with a main-assembly electroconductive memberelectrically connected with the main assembly of the image formingapparatus, the main-assembly electroconductive member being disposed inthe hole to ground said electrophotographic photosensitive drum, whereina contact position between said main-assembly electroconductive memberand said drum electroconductive member moves in interrelation with saidprojection being moved toward the hole by rotation of the drivingrotatable member when said projection is engaged with the hole of thedriving rotatable member.
 6. A process cartridge detachably mountable toan electrophotographic image forming apparatus, said process cartridgecomprising: an electrophotographic photosensitive drum; a non-circulartwisted projection having a cross-section with a plurality of cornerportions, said non-circular twisted projection being provided at onelongitudinal end of said electrophotographic photosensitive drum, andbeing engageable with a non-circular twisted hole having a cross-sectionwith a plurality of corner portions, the non-circular twisted hole beingdisposed at a central portion of a driving rotatable member of a mainassembly of the image forming apparatus; and a drum electroconductivemember provided on said projection and being electrically connected withsaid electrophotographic photosensitive drum, said drumelectroconductive member being contactable with a main-assemblyelectroconductive member electrically connected with the main assemblyof the image forming apparatus, the main-assembly electroconductivemember being disposed in the hole to ground said electrophotographicphotosensitive drum, wherein while said projection engages the hole andis being rotated, said main-assembly electroconductive member and saiddrum electroconductive member are integrally rotated while being incontact with each other.
 7. An electrophotographic image formingapparatus to which a process cartridge is detachably mountablecomprising: (i) a rotatable drive member; (ii) a non-circular twistedhole having a cross-section with a plurality of corner portions, saidnon-circular twisted hole being provided at a central portion of saidrotational drive member; (iii) a first electroconductive memberelectrically connected with a main assembly of said image formingapparatus; (iv) a process cartridge detachably mountable to a cartridgemounting portion, said process cartridge including: anelectrophotographic photosensitive drum; a non-circular twistedprojection having a cross-section with a plurality of corner portions,said non-circular twisted projection being provided at one longitudinalend of said electrophotographic photosensitive drum, and beingengageable with said non-circular twisted hole; and a secondelectroconductive member provided on said projection and beingelectrically connected with said electrophotographic photosensitivedrum, said drum electroconductive member being contactable with saidfirst electroconductive member to ground said electrophotographicphotosensitive drum, wherein a contact position between said secondelectroconductive member and said first electroconductive member movesin interrelation with said projection being moved toward said hole byrotation of said rotatable drive member when said projection is engagedwith said hole.
 8. An electrophotographic image forming apparatus towhich a process cartridge is detachably mountable, comprising: (i) arotational drive member; (ii) a non-circular twisted hole having across-section with a plurality of corner portions, said non-circulartwisted hole being provided at a central portion of said rotationaldrive member; (iii) a first electroconductive member electricallyconnected with a main assembly of said image forming apparatus, saidfirst electroconductive member being disposed in said hole; and (iv) aprocess cartridge detachably mountable to a cartridge mounting portionof said image-forming apparatus, said process cartridge including: anelectrophotographic photosensitive drum; a non-circular twistedprojection having a cross-section with a plurality of corner portions,said non-circular twisted projection being provided at one longitudinalend of said electrophotographic photosensitive drum, and beingengageable with said non-circular twisted hole, and a secondelectroconductive member contactable with said first electroconductivemember to electrically ground said electrophotographic photosensitivedrum, said second electroconductive member being provided on saidprojection and being electrically connected with saidelectrophotographic photosensitive drum, wherein while said projectionis in engagement with said hole and is being rotated, said secondelectroconductive member and said first electroconductive member areintegrally rotated while being in contact with each other.
 9. (canceled)